Because infidelity is relatively common among married men who work far from home, John Mbiti suggests polygamy is the best solution.
For [men who work a long distance from home] the most practical way of leading faithful lives, is to have one wife looking after the family on the land, while the other is with him in the distant town or city where he works. This to me seems like a very plausible, practical and understandable way of facing the situation of life honestly and fairly. It is more sensible and moral than chasing after prostitutes.
Sam Owusu concurs, posing the question: “Is it more Christian for a woman to commit infidelity or fornication than to become the second or third wife of a respected member of the community?”
We call this kind of argumentation the excluded middle. It offers two less than desirable options while leaving out a third (or middle) choice. For example: “Keeping a cabin full of slaves is not ideal, but it is better than letting your family starve.” Certainly leaving one’s family without food is sinful (1 Tim. 5:8), but so is slavery.
Mbiti appears to accept this logic, saying: “Certainly [polygamists] are better in so doing than in keeping prostitutes or concubines.” This statement assumes the situation is either/or, as though the menu has just two items: a monogamous marriage that succumbs to infidelity or a polygamous marriage. But there is a third option: chaste monogamy.
This leads us to the question of whether or not God will ever place us in a position where we have to choose between two forms of evil. First Corinthians 10:13 is clear: “No temptation has overtaken you that is not common to man. God is faithful, and he will not let you be tempted beyond your ability, but with the temptation he will also provide the way of escape, that you may be able to endure it.”
Here Scripture promises that if the only two apparent options are sinful, God will provide a third alternative–a way of escape. This verse does not mean that God will remove all temptation. Enticing women may still call from the shadows and neighbors may continue to offer their daughters to married men. But God can be trusted to provide an exit path for our own good.
In sum, then, I would answer the above question in two ways. First, no, polygamy is not a valid restraint to immorality because polygamy is itself immorality. I have argued elsewhere that polygamy is adultery. The explanation that spouses cannot commit adultery with one another is not convincing, as Jesus clearly taught the contrary.
Second, no, polygamy is not a valid restraint because it assumes polygamy is the lesser of two evils when in fact there is a feasible third option–faithfulness to one wife.